In today's society, I don't believe any outdoor cat is truly safe. It's an unfortunate truth that there are a lot of cruel people out there who don't like animals and any pet (cat or dog) left out on its own can be a target.
I'll give you an example of my mother's neighbor who used to let her 4 Chihuahua rescues run loose every day for an hour or so in her front yard -- which is completely fenced in and right in front of large picture windows. Well someone who evidently wasn't a dog lover threw poisoned food over the fence which one of the pups ate snd became violently ill. Though he survived the immediate life and death struggle, he had serious ongoing health problems and only lived about another year -- and this happened in a small town where all the neighbors still know each other.
My persian, Wuzzle, was found out on the street as a kitten. No one knows how long he was out there, but you would think that would stimulate his urge for the "wild side". While he's never made a bolt for the door in 4 years now, I think it's possible to give your cat a taste for the outdoors without the risks.
Wuzzle has two window perches where he can see out at any time. I have a bird feeder by one, so he can see the critters coming and going all day long. But they're safe and so is he. He'll also signal by scratching the blinds if he actually wants the window open for the full sensory experience. And basically, he get bored with it within a half hour at the most.
I guess the bottom line of what I'm saying is try to give your kitty alternative experiences to keep them happy and safe indoors. We're all busy and with the economy the way it is, maybe working several jobs -- but that extra 15 minutes you spend paying attention to your cat may save his or her life and you a great deal of grief.